Recently, such an image pickup unit type projector has been proposed which includes an image pickup camera for obtaining an image of a subject 6, and a projector main body 2 having the image pickup camera on the bottom and converting an image signal from the image pickup camera into image light to enlarge and project the image via a projection lens 3. The projector having this structure may obtain the image of the subject placed on the bottom of the projector main body 2. For example, see abstract and FIG. 1 of Japanese Patent Publication No. JP-A-2003-15216
When the distance between the camera of the projector and the subject is constant, the size of the image of the subject projected on a screen is kept constant. However, when an image of a display screen on a cellular phone is shot and projected on the screen, for example, the image size varies according to the size of the cellular phone, or the distance or the enlargement rate changes depending on the place of the cellular phone. These conditions may be controlled manually, but the process required for the control is troublesome.